1. Field of the Invention
The present invention relates to a lens barrel provided in image pickup apparatuses such as a film camera, a digital camera, and to an image pickup apparatus provided with the lens barrel.
2. Description of the Related Art
Conventionally, there is a known lens barrel provided with a zoom drive mechanism that regulates rotations of lens holding frames that hold lenses, respectively, by a rectilinear barrel, engages cam followers formed on the lens holding frames with cam grooves formed on a cam barrel, and moves the lens holding frames by rotating the cam barrel to move the lenses to predetermined positions.
A demand to increase a magnification in recent years tends to increase the full length under an extended condition and to enlarge a lens barrel. On the other hand, there is a demand to minimize a camera thickness under a lens retracted condition.
Although a multiple connection of short lens barrels may be effective to decrease the camera thickness under the lens retracted condition, there are many spatial limitations when cam grooves corresponding to the lens barrels are formed on a cam barrel without crossing.
On the other hand, a bayonet groove that is followed by a bayonet convex part provided on a rectilinear barrel is usually formed on an inner surface of a cam barrel. The positional relationship between the cam barrel and the rectilinear barrel in an optical axis direction is regulated because the bayonet convex part that fits into the bayonet groove contacts the wall surfaces of both sides in a width direction of the bayonet groove.
However, since cam grooves that are followed by cam followers of lens holding frames are formed on the inner surface of the cam barrel, an arrangement space of the bayonet groove is also restricted.
Therefore, a lens barrel in which a bayonet groove is formed in a circumferential direction so as to cross cam grooves formed on an inner surface of a cam barrel is proposed (see Japanese Laid-Open Patent Publication (Kokai) No. 2007-093999 (JP 2007-093999A)).
However, the technique of JP 2007-093999A requires that the bayonet groove crosses every cam groove so that the bayonet convex part straddles over a cam groove when the bayonet convex part passes through the cam groove. If the bayonet groove is not arranged in this manner, the bayonet convex part comes off the bayonet groove when passing through the cam groove, which disables the regulation of the positional relationship between the cam barrel and the rectilinear barrel in an optical axis direction. This reduces a degree of freedom for selecting positions of the cam grooves and the bayonet groove on the inner surface of the cam barrel, and increases difficulty to deal with various movements of the lens groups.